1. Field of the invention
The present invention relates to a method of, and an apparatus for, detecting or identifying microorganisms of interest contained in a specimen.
2. Related Background Art
Detection and identification of microorganisms have been hitherto made by culture examination. This is a method in which a plurality of culture mediums suited to the multiplication of microorganisms are prepared, samples are inoculated to the mediums so that the microorganisms are cultured, and the properties of the microorganisms thus grown are examined by various test methods such as morphological examination and biochemical examination.
In recent years, the agglutination method has also been developed, in which the agglutination of microorganisms, caused by antigen-antibody reaction using antibodies specific to various microorganisms, is recognized with the naked eye.
The culture method, however, takes a long time for the culture and also requires examinations on many items. In usual instances, it takes two or three days at minimum until the examinations are completed, so that, in some cases, patients have deceased before something has come out of the examination, as in diagnosis of infectious diseases. Some kinds of microorganisms also have the problems such that in some instances they are susceptible to death, can be cultured with difficulty, and thus can not be detected.
The agglutination method is a method that enables detection of even dead microorganisms, can be operated with relative simplicity, and can achieve a rapid examination. This, however, is a method in which the agglutination of microorganisms, caused by antigen-antibody reaction, is observed with the naked eye, so that microorganisms present in a small quantity can not be detected. The subjective views of the observer also tend to enter into his or her judgement, so that it may sometimes even occur that the results of examination are different when observed by different persons. Moreover, this method has the problems that the results of examination can not be objectively represented in numerical values or graphs and also the data obtained can not be stored.
On the other hand, beside these methods, a method is known in which individual fine particles in a specimen are optically measured using so-called flow cytometry techniques and the types of microorganisms are detected and classified based on its statistical tendency. Details thereof are disclosed in U.S. Pat. No. 4,661,913. The detection and classification method can be outlined as follows: Any correspondence of a statistical pattern of optical response, obtained by measurement, to a statistical pattern of known microorganisms, previously given, is sought after. When pattern forms are identical, the presence of a microorganism corresponding to the pattern is recognized.
In general, however, many kinds of fine particles other than the microorganisms of interest are present in the specimen unless purification is carried out. Hence, if other microorganisms or noise components that are similar to the microorganisms of interest in the measured values from the optical response are contained in the specimen, the noise components can not be distinguished from the microorganisms of interest. That is to say, it is difficult to form specifically only the microorganisms of interest into a pattern among many noise components. Even when the patterns are identical, it is impossible to confirm whether the pattern can really correspond to the microorganisms of interest whether it corresponds to the noise components. Thus, the method disclosed in U.S. Pat. No. 4,661,913 has the problems of low detection accuracy and poor reliability.